BAGHDAD, Iraq (CNN) -- A prominent local official was detained Thursday in southeastern Iraq during a new government offensive against militants along the Iranian border.
It is unclear why security forces seized Rafieh Abdul Jabbar, in Amara, the capital of Maysan province, a predominantly Shiite region.
Abdul Jabbar is a deputy provincial governor and the mayor of Amara, provincial police spokesman Col. Mehdi al-Asadi said.
Abdul Jabbar is a member of Shiite cleric Muqtada al-Sadr's political movement, a Sadrist spokesman said. Its fighters have battled with U.S. and Iraqi forces in recent months.
The governor of Maysan province, Adel Mohoder, also is affiliated with the Sadrists.
Sadrists said the U.S.-led coalition and Iraqi forces have been unfairly targeting al-Sadr's Mehdi Army militia, but the Iraqi government has said it is going after insurgents regardless of their affiliation.
Iraqi Prime Minister Nuri al-Maliki ordered security forces not to arrest anyone merely for being a Sadrist.
Al-Maliki stressed the offensive will only target criminals in hopes that Sadrist movement leaders will cooperate "in isolating these elements and reporting them to authorities in order to get rid of them."
Hours after the offensive began Thursday morning in Maysan, Iraq's Defense Ministry said 17 people had been detained, a weapons cache seized in Amara and weapons found near main roads and waterways.
Many people fled the province ahead of the crackdown, police said. Al-Asadi, the provincial police spokesman, said tribes in the region have been cooperating with security forces.
Al-Asadi said the action aims to "impose the law and to confront outlaws" and that curfews have been imposed in some parts of the province.
Al-Maliki had set a Wednesday deadline for "outlaws" in Maysan to hand in their weapons or face an offensive.
Al-Asadi said large amounts of weapons were seized and some wanted individuals detained during the four-day amnesty period.
The government is trying to stamp out militants and establish its authority in Shiite-dominated areas, particularly the oil-rich south, where rival Shiite militias have been battling for control.
As the spring began, al-Maliki cracked down on militants in the southern city of Basra and in Baghdad's large Sadr City slum. Followers of al-Sadr accused the government of trying to weaken their movement ahead of provincial elections.
Maysan province is believed to house members of al-Sadr's Mehdi Army who fled Basra and Sadr City after the government crackdowns.
The U.S. military said this week that the Amara push is "an Iraqi-initiated and -led operation. Coalition forces will provide support, as needed, much as they have in operations in and around Basra."
Al-Maliki also has stepped up operations against Sunni militants. Iraqi troops in and near the northern city of Mosul have been fighting al Qaeda in Iraq, the Sunni militant group.
U.S. forces detained 21 people Thursday in Sunni-dominated areas north of Baghdad. The operations took place in Mosul, Tarmiya, Bi'aj, Baiji and the Balad area.
Two roadside bombs were reported in predominantly Shiite areas of Baghdad on Thursday, two days after at least 63 people died in a blast in Hurriya, another Shiite neighborhood in the capital.
A bomb killed a civilian and wounded four others in the southwestern neighborhood of Bayaa. A roadside bomb also detonated near a popular restaurant on eastern Baghdad's Palestine Street, but no casualties were reported.
CNN's Jomana Karadsheh contributed to this report.